1. Field of the Invention
The present invention relates to a thermal transfer film having a coloring layer provided on a substrate film via an intermediate layer, more specifically, it relates to a thermal transfer film capable of providing a vivid print without generation of a void in a printed product, capable of applying preferably and stably the intermediate layer and the coloring layer to be formed on the substrate film, and further, having a classification leakage preventing function, and an image forming method using the same.
2. Description of the Related Art
Conventionally, as a thermal transfer recording medium to be used in a thermal transfer printer, a facsimile, or the like, a thermal transfer film provided with a coloring layer made from a thermally fusible ink on one surface of the substrate film has been used.
Conventional thermal transfer films have been produced by using a paper such as a condenser paper and a paraffin paper of about 10 to 20 xcexcm thickness, or a plastic film such as polyester and cellophane of about 3 to 20 xcexcm thickness as the substrate film, and applying a thermally fusible ink prepared by mixing a coloring agent such as a pigment and a dye to a binder, and optionally an additive such as a melting point lowering agent and a plasticizer onto the substrate film so as to provide a coloring layer. Moreover, some of the thermal transfer films comprise an intermediate layer between the substrate film and the coloring layer, adjusted so as to be fused by the energy of printing.
By heating and pressing a predetermined portion by a thermal head from the rear side of the substrate film, the coloring layer at a position corresponding to the printing part is fused so as to be transferred onto the transfer receiving material.
However, in the case of printing with the conventional thermal transfer film comprising the intermediate layer and the thermally fusible coloring layer provided on the substrate film, problems are involved in that the printed product can be blurred due to lack of characters or fine lines caused by a generated void and that the peeling sound generated at the time of peeling the thermal transfer film from the transfer receiving material is noisy. In order to print on a paper with a rough texture having a 50 seconds or less beck smoothness without generating a void, it is necessary to transfer the region of the coloring layer with the energy applied like pixels by means of a thermal head onto the receiving paper without generating a void (without remaining on the intermediate layer). In order to transfer the coloring layer entirely without generating a void in the receiving paper, it is effective to peel off the receiving paper and the thermal transfer film when the intermediate layer of the thermal transfer film provided with the coloring layer on the substrate film via the intermediate layer is melted so as to be in the liquid state with a high flowability. However, in equipments commonly used presently, such as a facsimile using a thermal transfer film, since there is a time interval between the moment when the printing energy is applied to the thermal transfer film after superimposing the transfer receiving material and the thermal transfer film and the moment when the thermal transfer film is peeled off from the transfer receiving material, even if an intermediate layer adjusted so as to be fused by the energy for printing is used, in general, it is cooled and aggregated again in the interval, or even if it is not aggregated, it is in the state with a low flowability.
Substances with the so-called supercooling property, having a freezing point lower than the melting point by 10xc2x0 C. or more have been known in various articles. Techniques concerning the thermal transfer film provided with a coloring layer on a substrate film via an intermediate layer using various substances having the supercooling property have been known. Examples thereof include Japanese Patent Application Laid-Open (JP-A) Nos. 61-235189, 61-286195, 62-9991, 62-82084, 63-302090, and 3-246094. In contrast, polycaprolactone resins having the supercooling property have been known in various articles. Techniques concerning the thermal transfer film provided with a coloring layer containing the polycaprolactone resin on the substrate film have been known. Examples thereof include Japanese Patent Application Laid-Open (JP-A) Nos. 59-230795, 60-122194, 60-122195, 61-185492, 62-59089, and 5-32073.
Moreover, techniques concerning the thermal transfer film provided with a coloring layer on a substrate film via an intermediate layer using the polycaprolactone resin have been known. For example, Japanese Patent Application Laid-Open (JP-A) No. 60-165291 discloses the use of a polycaprolactone resin in the intermediate layer for the purpose of printing for many times, and further, Japanese Patent Application Laid-Open (JP-A) No. 7-232483 discloses the use of a polycaprolactone having a 10,000 or less molecular weight in a primer layer for the purpose of high speed printing and smooth printing in a high temperature atmosphere.
However, according to the thermal transfer films using the intermediate layers of these techniques, the problem of blurring of the printed product due to lack of characters or fine lines caused by a generated void cannot be solved. Besides, since the molten state of the intermediate layer material continues for the time being after the thermal drying operation of the intermediate layer ink at the time of applying the ink to be the intermediate layer onto the substrate film, the base material surface and the intermediate layer surface of the thermal transfer film are bonded after being wound up after the application, and thus it is inconvenient. Furthermore, in the case of executing the hot melt coating method, which achieves the application at a low cost because it doesn""t require a solvent in applying the coloring layer onto the substrate film provided with the intermediate layer, since the polycaprolactone in the intermediate layer is melted by the heat of the heated and melted coloring layer ink so as to be a liquid, the coloring layer ink cannot be applied stably with a good surface quality, and thus it is inconvenient.
Accordingly, in order to improve and solve the above-mentioned disadvantages and problems, an object of the present invention is to provide a thermal transfer film capable of providing a vivid print without generation of a void in a printed product, capable of applying preferably and stably the intermediate layer and the coloring layer to be formed on the substrate film, and further, having a classification leakage preventing function, and an image forming method using the same.
In order to achieve the object, the present inventor discussed elaborately, paying attention to the melt viscosity of the thermally fusible substances having the supercooling property such as a polycaprolactone resin in the molten state at the time the transfer receiving material and the thermal transfer film are peeled off so as to reach to the present invention concerning the thermal transfer film. Moreover, the coating suitability of the intermediate layer containing the thermally fusible substance having the supercooling property, such as a polycaprolactone, and the overcoating suitability of the coloring layer onto the intermediate layer were discussed in detail so that a group of binder resins capable of improving the suitability thereof without casting an adverse effect on the melt viscosity of the thermally fusible substance having the supercooling property such as a polycaprolactone resin were found out so as to reach to the present invention concerning the thermal transfer film. Furthermore, the time interval from heating and recording the superimposed thermal transfer film and transfer receiving material until separating them was measured for discussion so as to reach to the present invention concerning an image forming method capable of printing vividly without generation of a void in the printed product.
That is, a first aspect of a thermal transfer film according to the present invention comprises a coloring layer formed on a substrate film via an intermediate layer, wherein the intermediate layer contains a polycaprolactone resin having a 100 mPaxc2x7s or more and 1,000 mPaxc2x7s or less melt viscosity at 75xc2x0 C., and a binder resin having a 130xc2x0 C. or more and 400xc2x0 C. or less extrapolation fuse starting temperature (the extrapolation fuse starting temperature defined in the JIS K7121-1987).
In a preferable embodiment of the first aspect, the thermal transfer film further has the following one or more features:
The binder resin is incompatible to the polycaprolactone resin;
The fuse peak temperature (the fuse peak temperature defined in the JIS K7121-1987) of the polycaprolactone resin is 45xc2x0 C. or more and 70xc2x0 C. or less, and the intermediate glass transitional temperature (the intermediate glass transitional temperature defined in the JIS K7121-1987) of the binder resin of the intermediate layer is higher than the fuse peak temperature of the polycaprolactone resin by 2xc2x0 C. or more;
The number average molecular weight of the binder resin is 8,000 or more and 1,000,000 or less;
The binder resin is a polyester resin;
The intermediate layer contains a carbon black;
The intermediate layer comprises a porous film comprising formed the binder resin and not to be thermally transferred, with a thermally fusible substance contained in the pores of the porous film;
The porous film further comprises a carbon black;
The melt viscosity at 100xc2x0 C. of the coloring layer is 150 mPaxc2x7s or more and 300 mPaxc2x7s or less; and/or,
The difference between the fuse peak temperature (the fuse peak temperature defined in the JIS K7121-1987) of the coloring layer and the fuse peak temperature (the fuse peak temperature defined in the JIS K7121-1987) of the polycaprolactone resin is 10xc2x0 C. or less.
An image forming method according to the first aspect of the present invention comprises the steps of superimposing a transfer receiving material onto the coloring layer surface of a thermal transfer film, heating and recording from the substrate film side like pixels by heating means, and separating the thermal transfer film and the transfer receiving material, wherein the thermal transfer film according to the first aspect of the present invention is used, and the time from recording the pixels to separating the thermal transfer film and the transfer receiving material is 0.05 second or more and 2 seconds or less.
In a preferable embodiment of the first aspect, the image forming method further has the following one or more features:
The heating means is an entire surface glaze type thermal head or a partial glaze type thermal head; and/or,
The energy for heating and recording is 10 mJ/mm2 or more and 35 mJ/mm2 or less.
A second aspect of a thermal transfer film according to the present invention comprises a coloring layer formed on a substrate film via an intermediate layer, wherein the intermediate layer contains a thermally fusible substance having a 100 mPaxc2x7s or more and 1,000 mPaxc2x7s or less melt viscosity at 75xc2x0 C., and a binder resin having a 150xc2x0 C. or more and 400 xc2x0 C. or less extrapolation fuse starting temperature (the extrapolation fuse starting temperature defined in the JIS K7121-1987), the thermally fusible substance having a crystallization peak temperature (the crystallization peak temperature defined in the JIS K7121-1987) which is lower than the fuse peak temperature (the fuse peak temperature defined in the JIS K7121-1987) of the same thermally fusible substance by 10xc2x0 C. to 50xc2x0 C.
In a preferable embodiment of the second aspect, the thermal transfer film further has the following one or more features:
The binder resin is incompatible to the thermally fusible substance;
The intermediate glass transitional temperature (the intermediate glass transitional temperature defined in the JIS K7121-1987) of the binder resin is higher than the fuse peak temperature (the fuse peak temperature defined in the JIS K7121-1987) thermally fusible substance by 2xc2x0 C. or more;
The number average molecular weight of the binder resin is 8,000 or more and 1,000,000 or less;
The binder resin is a polyester resin;
The intermediate layer contains a carbon black;
The intermediate layer comprises a porous film comprising the binder resin and not to be thermally transferred, with a thermally fusible substance contained in the pores of the porous film;
The porous film further comprises a carbon black;
The melt viscosity at 100xc2x0 C. of the coloring layer is 150 mPaxc2x7s or more and 300 mPaxc2x7s or less; and/or,
The difference between the fuse peak temperature (the fuse peak temperature defined in the JIS K7121-1987) of the coloring layer and the fuse peak temperature (the fuse peak temperature defined in the JIS K7121-1987) of the thermally fusible substance is 10xc2x0 C. or less.
An image forming method according to the second aspect of the present invention comprises the steps of superimposing a transfer receiving material onto the coloring layer surface of a thermal transfer film, heating and recording from the substrate film side like pixels by heating means, and separating the thermal transfer film and the transfer receiving material, wherein the thermal transfer film according to the second aspect of the present invention is used, and the time from recording the pixels to separating the thermal transfer film and the transfer receiving material is 2 seconds or less.
In a preferable embodiment of the second aspect, the image forming method further has the following one or more features:
The heating means is an entire surface glaze type thermal head or a partial glaze type thermal head; and/or,
The energy for heating and recording is 10 mJ/mm2 or more and 35 mJ/mm2 or less.
A third aspect of a thermal transfer film according to the present invention comprises a coloring layer formed on a substrate film via an intermediate layer, wherein the intermediate layer contains a polycaprolactone resin having a 100 mPaxc2x7s or more and 1,000 mPaxc2x7s or less melt viscosity at 75xc2x0 C., and a non-transferable binder resin having a 130xc2x0 C. or more and 400xc2x0 C. or less softening temperature (the softening temperature measured by the ring and ball method defined in the JIS K2207-1980).
In a preferable embodiment of the third aspect, the thermal transfer film further has the following one or more features:
The binder resin is incompatible to the polycaprolactone resin;
The fuse peak temperature (the fuse peak temperature defined in the JIS K7121-1987) of the polycaprolactone resin is 45xc2x0 C. or more and 70xc2x0 C. or less, and the intermediate glass transitional temperature (the intermediate glass transitional temperature defined in the JIS K7121-1987) of the binder resin of the intermediate layer is higher than the fuse peak temperature of the polycaprolactone resin by 2xc2x0 C. or more;
The number average molecular weight of the binder resin is 8,000 or more and 1,000,000 or less;
The binder resin is a resin having a benzene ring structure;
The binder resin is a polyester resin;
The intermediate layer contains a carbon black;
The intermediate layer comprises a porous film comprising the binder resin and not to be thermally transferred, with a polycaprolactone resin contained in the pores of the porous film;
The porous film further comprises a carbon black;
The melt viscosity at 100xc2x0 C. of the coloring layer is 150 mPaxc2x7s or more and 300 mPaxc2x7s or less; and/or,
The difference between the fuse peak temperature (the fuse peak temperature defined in the JIS K7121-1987) of the coloring layer and the fuse peak temperature (the fuse peak temperature defined in the JIS K7121-1987) of the polycaprolactone resin is 10xc2x0 C. or less.
An image forming method according to the third aspect of the present invention comprises the steps of superimposing a transfer receiving material onto the coloring layer surface of a.thermal transfer film, heating and recording from the substrate film side like pixels by heating means, and separating the thermal transfer film and the transfer receiving material, wherein the thermal transfer film according to the third aspect of the present invention is used, and the time from recording the pixels to separating the thermal transfer film and the transfer receiving material is 0.05 second or more and 2 seconds or less.
In a preferable embodiment of the third aspect, the image forming method further has the following one or more features:
The heating means is an entire surface glaze type thermal head or a partial glaze type thermal head; and/or,
The energy for heating and recording is 10 mJ/mm or more and 35 mJ/mm2 or less.
A fourth aspect of a thermal transfer film according to the present invention comprises a coloring layer formed on a substrate film via an intermediate layer, wherein the intermediate layer contains a thermally fusible substance having a 100 mPaxc2x7s or more and 1,000 mPaxc2x7s or less melt viscosity at 75xc2x0 C., and a non-transferable binder resin having a 130xc2x0 C. or more and 400xc2x0 C. or less softening temperature (the softening temperature measured by the ring and ball method defined in the JIS K2207-1980), the thermally fusible substance having a crystallization peak temperature (the crystallization peak temperature defined in the JIS K7121-1987) which is lower than the fuse peak temperature (the fuse peak temperature defined in the JIS K7121-1987) by 10xc2x0 C. to 50xc2x0 C.
In a preferable embodiment of the fourth aspect, the thermal transfer film further has the following one or more features:
The binder resin is incompatible to the thermally fusible substance;
The intermediate glass transitional temperature (the intermediate glass transitional temperature defined in the JIS K7121-1987) of the binder resin is higher than the fuse peak temperature (the fuse peak temperature defined in the JIS K7121-1987) of the thermally fusible substance by 2xc2x0 C. or more.
The number average molecular weight of the binder resin is 8,000 or more and 1,000,000 or less;
The binder resin is a resin having a benzene ring structure;
The binder resin is a polyester resin;
The intermediate layer contains a carbon black;
The intermediate layer comprises a porous film comprising the binder resin and not to be thermally transferred, with a thermally fusible substance contained in the pores of the porous film;
The porous film further comprises a carbon black;
The melt viscosity at 100xc2x0 C. of the coloring layer is 150 mPaxc2x7s or more and 300 mPaxc2x7s or less; and/or
The difference between the fuse peak temperature (the fuse peak temperature defined in the JIS K7121-1987) of the coloring layer and the fuse peak temperature (the fuse peak temperature defined in the JIS K7121-1987) of the thermally fusible substance is 10xc2x0 C. or less.
An image forming method according to the fourth aspect of the present invention comprises the steps of superimposing a transfer receiving material onto the coloring layer surface of a thermal transfer film, heating and recording from the substrate film side like pixels by heating means, and separating the thermal transfer film and the transfer receiving material, wherein the thermal transfer film according to the fourth aspect of the present invention is used, and the time from recording the pixels to separating the thermal transfer film and the transfer receiving material is 2 seconds or less.
In a preferable embodiment of the fourth aspect, the image forming method further has the following one or more features:
The heating means is an entire surface glaze type thermal head or a partial glaze type thermal head; and/or,
The energy for heating and recording is 10 mJ/mm2 or more and 35 mJ/mm2 or less.
According to the present invention with the above-mentioned configuration, it was found out that since the intermediate layer comprising a specific binder resin and a polycaprolactone resin or a thermally fusible substance is in the state with the interface with respect to the coloring layer fused owing to the supercooling property of the components as well as in the low viscosity state even if the portion applied with the printing energy is cooled down to some extent in the interval from printing to the peel-off, the coloring layer can be peeled off from the thermal transfer film by a low peeling force so as to be transferred onto the transfer receiving material, and thus remaining of the coloring layer at the portion applied with the printing energy causing the cohesive failure within the layer, on the intermediate layer can be prevented so that the thermal transfer film can be peeled off, so that the interface between the coloring layer and the intermediate layer can be separated. Moreover, it was also found out that the coloring layer in the region applied with the energy can be transferred onto the transfer receiving material without a void, and thus a preferable printed product can be obtained with little void even with respect to a rough paper as the transfer receiving material.